This invention relates to a method and apparatus of electrophotography of the kind in which charging and original image projection are made to a photosensitive element having a photoconductive layer to form an electrostatic latent image on the surface thereof and the latent image is developed by a developing agent to produce a toner image.
It has generally been required in the method and apparatus of the kind specified that an operation, such as control of the voltage applied to the photosensitive element, adjustment of the position of the charging device or adjustment of the rate of projection of the original image is made to provide a charging voltage suitable for the quality of the photosensitive element used, thereby preventing the formation of a stained background and producing an image having a good tone. When a developing device is used in which there is provided a mixture of toner and carrier, such as iron powder, it is necessary to prevent affixation of the carrier to the photosensitive element to adversely affect the toner image and such an operation as is described above is desirable to minimize this adverse affection. There has, however, been a relatively large dispersion of the quality of the photosensitive elements produced by now and the degree of this disposition of the quality of the elements is so great as to be incapable of being compensated by the above operation, so that a relatively large amount of the photosensitive elements unfitted to conventional electrophotographic methods and apparatus as to be scrapped.